Wafer to wafer, chip to wafer, or ship to chip (all used interchangeable herein) bonding can require high precision alignment and high precision bonding. Conventional precision alignment and bonding of wafers has consisted of visual alignment utilizing microscopes.
Visual alignment can be useful when one of the wafers is transparent. However, when both of the wafers are opaque, high precision alignment is difficult. Conventional alignment techniques can have an alignment precision in a range from 5 to 10 micrometers.
As features scale down on the wafers, high precision alignment becomes more difficult. There is a need for high precision wafer bonding technique that can align wafer features to within 100 nanometers or less.